Chemical sensors such as gas sensors, for example, in many cases consist of materials which are not chemically inert. On the one hand, the metal or Si substrates and the metal conductors, and on the other hand the active sensor layers such as metal oxides, for example, are attacked by aggressive chemicals (e.g. acids, HF, etc.). One site of application having such a chemically aggressive environment is the interior of an Li ion battery cell. Here, e.g. the electrolyte consists of fluorine-containing conducting salts dissolved in organic solvents (typically carbon dioxide esters).